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The Very Large Hadron Collider

Description: I present some of the current ideas about a Very Large Hadron Collider [1] which could eventually extend the high energy frontier beyond that of the Large Hadron Collider (LHC) or any other machine seriously conceived at this time.
Date: February 16, 1999
Creator: Albrow, Michael G.
Partner: UNT Libraries Government Documents Department

Next to leading order three jet production at hadron colliders

Description: I present results from a next-to-leading order event generator of purely gluonic jet production. This calculation is the first step in the construction of a full next-to-leading order calculation of three jet production at hadron colliders. Several jet algorithms commonly used in experiments are implemented and their numerical stability is investigated. A numerical instability is found in the iterative cone algorithm which makes it inappropriate for use in fixed order calculations beyond leading order.
Date: May 1, 1997
Creator: Kilgore, W.B.
Partner: UNT Libraries Government Documents Department

The theory of hadronic systems. Annual progress report

Description: This report briefly discusses progress on the following topics: isospin breaking in the pion-nucleon system; the np charge-exchange reaction; energy dependence of pion DCX; pion absorption in nuclei; quantum effects in inclusive reactions; and pion scattering from polarized nuclei.
Date: April 8, 1994
Creator: Gibbs, W.R.
Partner: UNT Libraries Government Documents Department

An update on strong W{sub L}W{sub L} scattering at the LHC

Description: The author summarizes an update on the study for a strongly interacting electroweak symmetry breaking sector via longitudinal vector boson scattering at the 14 TeV Large Hadron Collider. In the update, the decay mode ZZ {yields} l{sup +}l{sup {minus}}{nu}{bar {nu}} and a new vector-resonance signal via q{bar q} {yields} V {yields} W{sup +}W{sup {minus}}/W{sup {+-}}Z are also included.
Date: March 1, 1995
Creator: Cheung, K.
Partner: UNT Libraries Government Documents Department

Constraints on q{bar q}{gamma}{gamma} contact interactions at future hadron colliders

Description: The author explores the capability of the Tevatron and LHC as well as other future hadron colliders to place limits on the possible existence of flavor-independent q{bar q}{gamma}{gamma} contact interactions which can lead to an excess of high p{sub t} diphoton events with large invariant masses. Constraints on the corresponding e{sup +}e{sup {minus}}{gamma}{gamma} contact interaction already exist from LEP. In the case of hadron colliders, strong constraints on the scale associated with such interactions are achievable in all cases, e.g., of order 0.9(3) TeV at TeV33(LHC).
Date: September 1, 1996
Creator: Rizzo, T.G.
Partner: UNT Libraries Government Documents Department

Tolerable systematic errors in Really Large Hadron Collider dipoles

Description: Maximum allowable systematic harmonics for arc dipoles in a Really Large Hadron Collider are derived. The possibility of half cell lengths much greater than 100 meters is justified. A convenient analytical model evaluating horizontal tune shifts is developed, and tested against a sample high field collider.
Date: December 1, 1996
Creator: Peggs, S. & Dell, F.
Partner: UNT Libraries Government Documents Department

Beam tube vacuum in low field and high field very large hadron colliders

Description: Bounds on the beam tube gas pressure and the required pumping speed are estimated for {approximately} 2 T low field (LF) and - 12 T high field (HF) 100 TeV center-of-mass hadron colliders. In both cases photodesorption by synchrotron radiation is the dominant source of gas. Assuming beam-gas scattering limited luminosity lifetime five times the IP scattering lifetime, the required CO equivalent beam tube pressure is 0.25 ntorr for LF and 1.8 ntorr for HF, ambient room temperature equivalent. The CO equivalent pumping speeds required to achieve this pressure within a reasonable beam conditioning time (a few tenths of an operational year at design intensity) are estimated to be {approximately} 300 I/s-m for LF and - 40 I/s-m for HF. For the LF case with a superferric warm and a distributed NEG plus lumped ion or cryo pump system is considered. The size of antechamber needed, ID- 6 cm, requires that it be located outside the - 2 cm C-coil magnet gap. Lumped pumps for pumping CH{sub 4} need to be spaced at - 20 in intervals on the antechamber. For the HF case the likely beam tube temperature .is 15-20 K and cryopumping with a beam screen system is considered. The necessary pumping speed can be achieved with slots covering {approximately} 2 per cent of the beam screen surface.
Date: October 1, 1996
Creator: Turner, W.C.
Partner: UNT Libraries Government Documents Department

Crab crossing in a large hadron collider

Description: Since its invention by Palmer in 1988, crab crossing has been explored by many people for both linear and storage ring collides to allow for an angle crossing without a loss of luminosity. Various crab crossing scenarios have been incorporated in the design of newly proposed linear collides and {Beta}-factory projects. For a hadron collider, this scheme can also be employed to lower {Beta}* at the interaction point for a higher luminosity. In this paper, we first review the principle and operational requirements of various crab crossing schemes for storage ring collides. A Hamiltonian formalism is developed to study the dynamics of crab crossing and the related synchro-betatron coupling. Requirements are obtained for the operational voltage and frequency of the crab cavities, and for the accuracy of voltage matching and phase matching of the cavities. For the recently proposed high-field hadron collider, a deflection crabbing scheme can be used to reduce {Beta}* from 0. 1 m to 0.05 m and below, without a loss of luminosity due to angle crossing. The required voltage of the storage rf system is reduced from 100 MV to below 10 MV. With the same frequency of 379 MHz operating in a transverse mode, the required voltage of the crab cavities is about 3.2{approximately}4.4 MV. The required accuracy of voltage and betatron-phase matching is about 1 %.
Date: December 1, 1996
Creator: Wei, Jie
Partner: UNT Libraries Government Documents Department

Hadronic production of S-wave and P-wave charmed beauty mesons via heavy quark fragmentation

Description: At hadron colliders the dominant production mechanism of ({bar b}c) mesons with large transverse momentum is due to parton fragmentation. The authors compute in a model-independent way the production rates and transverse momentum spectra for S-wave and P-wave ({bar b}c) mesons at the Tevatron via the direct fragmentation of the bottom antiquark as well as the Altarelli-Parisi induced gluon fragmentation. Since all the radially and orbitally excited ({bar b}c) mesons below the BD flavor threshold will cascade into the pseudoscalar ground state B{sub c} through electromagnetic and/or hadronic transitions, they all contribute to the inclusive production of B{sub c}. The contributions of the excited S-wave and P-wave states to the inclusive production of B{sub c} are 58 and 23%, respectively, and hence significant.
Date: February 1, 1995
Creator: Cheung, K. & Yuan, Tzu Chiang
Partner: UNT Libraries Government Documents Department

Discovery mass reach for excited quarks at hadron colliders

Description: If quarks are composite particles then excited states are expected. We estimate the discovery mass reach as a function of integrated luminosity for excited quarks decaying to dijets at the Tevatron the mass reach is 0.94 TeV for Run 11 (2 fb{sup -1}) and 1. 1 TeV for TeV33 (30 fb{sup -1}). At the LHC the mass reach is 6.3 TeV for 100 fb{sup -1}. At a VLHC with a center of mass energy {radical}s, of 50 TeV (200 TeV) the mass reach is 25 TeV (78 TeV) for an integrated luminosity of 10{sup 4} fb{sup -1}. However, an excited quark with a mass of 25 TeV would be discovered at a hadron collider with {radical}s = 100 TeV and an integrated luminosity of 13 fb{sup -1}, illustrating a physics example where a factor of 2 in machine energy is worth a factor of 1000 in luminosity.
Date: September 10, 1996
Creator: Harris, R.M.
Partner: UNT Libraries Government Documents Department

Very large hadron colliders

Description: Issues pertaining to the next generation (post LHC) Hadron Colliders have been addressed over the past several years at workshops at Indiana, Indianapolis, and more recently at Snowmass. Although no attempt has been made to produce a detailed parameter set, most work has addressed energies in the range of 80-100 TeV centre-of-mass with a peak luminosity of 10{sup 34} cm{sup -2} s{sup -1}. This is sufficient to illuminate the potential problems associated with this class of machines. There have been two distinct design concepts that have been examined; the low-field and high-field options. It is significant to note that while an SSC-like approach to access this energy range is technically feasible the cost of such a device is deemed prohibitive. There is general agreement that new technologies are necessary to achieve a cost breakthrough and as such that the dominant technical challenges for the future are driven by cost considerations, unlike linear or muon colliders, where cost is merely important the organizing committee at Snowmass challenged the sub-group with a cost goal of $50M per Tev, and although neither option is sufficiently mature at this point to attempt any meaningful cost estimate, this figure gives an indication of the potential challenge facing the machine designers. The basic accelerator concept for an VLHC is perceived to be similar to today`s machines: long repetitive arcs in a 2-in-1 magnet scheme with a few interaction regions encompassing the experimental regions and accelerator utilities. While a wide variety of design have been examined it has not been deemed terribly important to produce any integrated VLHC design at this point in time. This report briefly examines these concepts.
Date: December 31, 1996
Creator: Harrison, M.
Partner: UNT Libraries Government Documents Department

Flat beams in a 50 TeV hadron collider

Description: The basic beam dynamics of a next generation 50 x 50 TeV hadron collider based on a high field magnet approach have been outlined over the past several years. Radiation damping not only produces small emittances, but also flat beams, just as in electron machines. Based on {open_quotes}Snowmass 96{close_quotes} parameters, we investigate the issues associated with flat beams in very high energy hadron colliders.
Date: August 1, 1997
Creator: Peggs, S.; Harrison, M.; Pilat, F. & Syphers, M.
Partner: UNT Libraries Government Documents Department

Threshold resummation and the total cross section for top quark production

Description: We discuss the motivation for resummation of the effects of initial-state soft gluon radiation, to all orders in the strong coupling strength, for processes in which the near-threshold region in the partonic subenergy is important. We summarize our calculation of the total cross section for top quark production at hadron colliders. Comments are included on the differences between our treatment of subleading logarithmic terms and other methods.
Date: June 12, 1997
Creator: Berger, E.L. & Contopanagos, H.
Partner: UNT Libraries Government Documents Department

The theory of hadronic systems. Annual progress report

Description: This report briefly discusses progress on the following topics: isospin breaking in the pion-nucleon system; direct capture of pions into deeply bound atomic states; knock out of secondary components in the nucleus; study of the radii of neutron distributions in nuclei; the hadronic double scattering operator; transparency in pion production; asymmetry in pion scattering and charge exchange from polarized nuclei; the mechanism of pion absorption in nuclei; the neutron-proton charge-exchange reaction; modification of the fundamental structure of nucleons in nuclei; and antiproton annihilation in nuclei.
Date: April 12, 1993
Creator: Gibbs, W.R.
Partner: UNT Libraries Government Documents Department

The theory of hadronic systems

Description: This report briefly discusses progress on the following topics: isospin breaking in the pion-nucleon system; subthreshold amplitudes in the {pi}N system; neutron-proton charge-exchange; transparency in pion production; energy dependence of pion DCX; direct capture of pions into deeply bound atomic states; knock out of secondary components in the nucleus; radii of neutron distributions in nuclei; the hadronic double scattering operator; pion scattering and charge exchange from polarized nuclei; pion absorption in nuclei; modification of nucleon structure in nuclei; and antiproton annihilation in nuclei.
Date: March 16, 1995
Creator: Gibbs, W.R.
Partner: UNT Libraries Government Documents Department

Parton distributions with high energy proton beams

Description: The opportunities for using high energy proton beams to advance our current knowledge in parton distributions are discussed. Highlights from some Fermilab dimuon production experiments with 800 GeV proton beams are presented. Possible future directions are discussed.
Date: December 31, 1996
Creator: Peng, J.C.
Partner: UNT Libraries Government Documents Department

Interaction region analysis for a high-field hadron collider

Description: The primary goal of the interaction region (IR) is to demagnify the transverse beam dimension to a small spot size at the interaction point (IP) to reach the required luminosity. With an experimental drift space of {+-}25 m and a quadrupole focusing strength of 360 T/m at the triplets, a {Beta}* of 0.1 m can be achieved at a beam energy of 50 TeV. Only two families of sextupoles are needed to globally correct the chromaticity. Since the momentum spread of the beam is small ({sigma}{sub p} {approx} 2 x 10{sup -5}), a relatively large (about 20) linear chromaticity can be tolerated so that higher-order chromatic aberration produced by the low-{Beta}* optics is negligible. With a crossing angle of 70 {mu}r and a beam separation of 5 {sigma}, the required minimum aperture of the triplet magnets is about 3 cm. The luminosity reduction resulted from such a crossing angle is about 13%. Crab crossing can be used to further reduce {Beta}* to below 0.05 m. At the same time, luminosity degradation caused by the angle crossing is eliminated. With crab cavities positioned near the triplet operating at a voltage of a few MV, the required voltage of the 379 MHz storage rf system can be reduced from the nominal 100 MV to below 10 MV. The requirements on the accuracy of the positioning of the crab cavities and the operating voltage are both moderate. More than two families of sextupoles are needed for global chromatic compensation only when, {Beta}* approaches 0.05 m and below.
Date: December 1, 1996
Creator: Wei, Jie; Peggs, S.G. & Goderre, G.P.
Partner: UNT Libraries Government Documents Department

Disoriented chiral condensates in hadron-hadron collisions

Description: The authors review recent progress in the description and understanding of disoriented chiral condensates. Certain important unsolved issues are underlined, and the preliminary results of the program of investigation of these issues in the framework of the classical linear sigma model are reported. They also briefly review a formalism which could be useful at the full non-equilibrium quantum field theory level of analysis.
Date: September 1, 1996
Creator: Amelino-Camelia, G.; Bjorken, J.D. & Larsson, S.E.
Partner: UNT Libraries Government Documents Department